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Dunlavy SC-IV Tweeter Problem and Questions
Dunlavy SC-IV Tweeter Problem and Questions
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Old 1st December 2007, 07:07 AM   #1
klimaudio is offline klimaudio  United States
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Default Dunlavy SC-IV Tweeter Problem and Questions

I have a pair of Dunlavy SC-IV and I have had to replace one blown tweeter when I purchased them initially a few years ago. The tweeter is starting to distort in one of the speakers at a relatively low SPL, and it needs to be replaced. I'm going to take the tweeter out and see if it is the original Dunlavy driver (Vifa D27TG-35-06) or the one I already replaced.

Upgrade time? I'm thinking I want to replace both tweeters with something different. I know that tweeters in these speakers tend to blow fairly easy due to the 1st order crossover and played at a higher than ususal SPL (which I'm sure is what happened to the original driver I had to replace), and I woud like something that sounds the same but is a little more robust. I plan on doing some audio server based DRC, and I know that I will probably end up at some point sending some nasty signals into my speakers...and toasting the tweeters.

Now onto the questions....

Have any Dunlavy owners on this board substituted a different tweeter on their SC-IV (or any other Dunlavy that uses that Vifa tweeter)?

Does anyone have a schematic of the crossover for the SC-IV?

Has anyone ever completely bypassed the passive crossovers and converted their Dunlavy's to a fully active crossover loudspeaker? (I know that may be heresy to some people, but I know I can eek out a little better performance with a little DSP magic.)

By the way, this is my first post on the board. I have been trolling the site for awhile, and I am very impressed by the many DIY projects I've seen on this site. You people have done some incredible work...I'm so happy to see that there are still this many audio nuts around.
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Old 1st December 2007, 05:47 PM   #2
KBK is offline KBK  Canada
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The problem seems to be the crossover design. I've run into this exact problem before on this exact model.

We went through every single possible source of the issue. The system in our case, was with an active room correction system being involved and some highly unusual speaker cables, as well. After over 1 year of going over every single possible issue, I walked away, as I was not directly involved in the sale nor service of the system. I personally concluded that the crossover design was at fault. There is a resonance issue in crossover for the tweeter, or energy feeding back from other drivers via combined grounding. IMHO. It needs to be re-designed. The same tweeters were blown three times, even after the 'newer' tweeters were installed as a potential fix. How this speaker design ever made it out the door with this flaw is a total mystery to me. It may have come down to a constructional issue, with the given technician who made that exact unit.

Or, its simply a fact that John made those designs with too much bottom end (low frequencies) for the tweeters to handle.

The crossovers will likely have to be pulled and compared, if the only the one tweeter is failing. We are hoping this is the final answer on this particular issue, involving this series of Dunlavy speakers. You are not alone.
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Old 1st December 2007, 06:06 PM   #3
Magnetar is offline Magnetar  United States
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The pair I had required a box of replacement diaphrams at all times. I used them like fuses.. expensive ones. they are a poor design if you want spl out of them. I sold mine with zero regrets. If you are going to triamp build your own speaker. The pair of home brew speakers I listen to right now are wayyyyyy better then the sc4, and yep I think the dunlavys were pretty good for store bought high end stuff other than a terribly designed crossover
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Old 2nd December 2007, 12:49 AM   #4
klimaudio is offline klimaudio  United States
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Does anyone know of a source for the replacement diphrams and voice coil for this speaker? If I had a couple extras, I would feel a little more confident with my room correction adventures.
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Old 2nd December 2007, 08:02 AM   #5
klimaudio is offline klimaudio  United States
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Nevermid the last question. I found a place that sells them for $10 a pop (no pun intended). I'll ask them how many they have in stock and buy a bunch. I'm hoping they have them in stock.

I took apart the orignal tweeter I had to replace, and saw that it is easy to replace the diaphragm / vc (3 screws, pop it out, pop in the new one). I wish I would have known this when I bought my first replacement driver.....I would have bought a ton of these replacements diaphragms instead.
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Old 2nd December 2007, 12:37 PM   #6
Magnetar is offline Magnetar  United States
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Originally posted by klimaudio
Nevermid the last question. I found a place that sells them for $10 a pop (no pun intended). I'll ask them how many they have in stock and buy a bunch. I'm hoping they have them in stock.

I took apart the orignal tweeter I had to replace, and saw that it is easy to replace the diaphragm / vc (3 screws, pop it out, pop in the new one). I wish I would have known this when I bought my first replacement driver.....I would have bought a ton of these replacements diaphragms instead.
I think Madisound has them. I used to drive mine with either 200 watt PP tube amps or 700 watt Classe' mono amp - after you see how easy it is to replace the dome and buy them, they become fuses! I bet you'll be poppin them more often now ; )

You could fuse them with an in line fuse to the tweeter, maybe start out at .5 amp and work your way up - that would be cheaper and easier
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Old 2nd December 2007, 03:56 PM   #7
klimaudio is offline klimaudio  United States
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First off....thanks for mentioning the replacement diaphrams!!! I forgot that those were even offered.

I'm powering mine with 2 AETechron amplifiers (used for hospital MR equipment).....I'm guessing around 300-350 watts per channel. I've never measured them, but I know I like the way they sound.

As you mentioned how easy it was to replace the diaphram....I was shocked to see it was that easy. I was just a little nervous about messing with the drivers, and I didn't want to order a diaphram to find out it was overly complicated and sensitive to allignment. I was very pleased to find out that Vifa made it easy enough that even I could do it!

I didn't see them on Madisound's site (first place I checked..where I bought my replacement driver). I'm going to call them on Monday. After googling, I found a place in Cali that has (hopefully not "had") them.

Anyone ever purchased from this company?

http://www.speakercity.com

Now that I'm going the diaphragm replacement route, I have a couple more questions. Dunlavy matched drivers when the speakers were built.....are there huge differences between the magnet structures with these tweeters? Are the replacement diaphragms fairly consistent between each other?

Since these seem to use ferrofluid (or some type of non-conductive grease?).....are there any recommedations as to what kind to use and how much of it I should use when I replace the diaphram?

Any recommendations on rebuilding these drivers would be appreciated.
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Old 4th May 2010, 12:16 AM   #8
JAZZY JESS is offline JAZZY JESS  United States
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Quote:
Originally Posted by KBK View Post
The problem seems to be the crossover design. I've run into this exact problem before on this exact model.

We went through every single possible source of the issue. The system in our case, was with an active room correction system being involved and some highly unusual speaker cables, as well. After over 1 year of going over every single possible issue, I walked away, as I was not directly involved in the sale nor service of the system. I personally concluded that the crossover design was at fault. There is a resonance issue in crossover for the tweeter, or energy feeding back from other drivers via combined grounding. IMHO. It needs to be re-designed. The same tweeters were blown three times, even after the 'newer' tweeters were installed as a potential fix. How this speaker design ever made it out the door with this flaw is a total mystery to me. It may have come down to a constructional issue, with the given technician who made that exact unit.

Or, its simply a fact that John made those designs with too much bottom end (low frequencies) for the tweeters to handle.

The crossovers will likely have to be pulled and compared, if the only the one tweeter is failing. We are hoping this is the final answer on this particular issue, involving this series of Dunlavy speakers. You are not alone.
Certainly true. All of the Dunlavy speakers have that problem. Some more than others due to the all the LCR networks needed to achieve that +/- 1 dB. If you look at any Dunlavy crossover schematics, They are not even true first order, Hey man but don't blame the technician; I fought with John so many times about this issue.
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Old 4th May 2010, 05:31 AM   #9
David Gatti is offline David Gatti  Australia
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You may want to consider something like a Morel MDT33 as a more robust replacement.
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Old 4th May 2010, 01:42 PM   #10
dry martini is offline dry martini  United States
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If anyone's felt surrounds for the tweeter are getting long in the tooth, I have replaced quite a few. Just lemme know. Cheers
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